1. Field of the Invention
The present invention relates to a device and method capable of converting a position signal into a frequency signal, and more particularly relates to a device and method capable of converting a position signal into a frequency signal using a photoelectric position sensitive detector (PSD).
2. Description of the Related Art
In the prior art of a photoelectric system capable of displaying a position signal, two terminals of a PSD output two photocurrents when a light spot is detected by the PSD. FIG. 1 shows a device and method of calculating a light spot position according to the prior art. As shown in FIG. 1, two photocurrents (I1, I2) are respectively converted into two voltage signals (Vx1, Vx2) by two operational amplifiers (OP AMP) A1 and A2. An adder outputs a (Vx1+Vx2) voltage signal; a subtracter outputs a (Vx2-Vx1) voltage signal; and a divider outputs a (Vx2-Vx1)/(Vx1+Vx2) i.e. (I2-I1)R1/(I1+I2)R1! voltage signal. The (Vx2-Vx1)/(Vx1+Vx2) voltage signal will be converted into a signal via an analog-to-digital (A/D) converter and a single chip microprocessor. Then a signal corresponding to the light spot falling on PSD will be shown on an LCD panel.
However, this kind of prior art has the following disadvantages. First, it is too complicated due to usage of a lot of circuits, for example, a divider, or an A/D converter . . . etc. Second, a DC drift signal due to DC amplifier circuit will influence the displaying result.